Daily inspection and maintenance regeneration method of pH meter electrode
Check the usage status of the pH meter electrode, whether it can be used, and the methods of maintaining, cleaning and regenerating the electrode according to the situation are as follows. Anhui Secco Environmental Protection Technology Co., Ltd. All rights reserved. PH meter inspection: 1. General inspection method of glass electrode
(1) Check the zero potential and set the pH meter to the "mV" measurement range. Insert the glass electrode and the reference electrode into the buffer solution with pH=6.86. The reading of the instrument should be about -50~50mV. an examination
(2) Check the slope connection
1. Then measure the mV value of the buffer solution with pH=4.00 or pH=9.18, and calculate the slope of the electrode. The relative slope of the electrode should generally be combined with technical indicators. Notice:
1) The method of checking the zero potential value of the electrode is only for the glass electrode whose equipotential point is 7. If the equipotential point of the glass electrode is not 7, it will be different.
2) For some pH meters, when the calibration and adjustment can meet the requirements, and the above inspection results are not out of range, the electrode can be used.
3) For some smart pH meters, you can directly refer to the zero potential and slope values obtained from the calibration results of the instrument.
2. Inspection method of reference electrode
(1) The internal resistance test method uses a laboratory conductivity meter. One end of the electrode socket of the conductivity meter is connected to a reference electrode, and the other end is connected to a metal wire. The reference electrode and the metal wire are immersed in the solution at the same time. The measured internal resistance Should be less than 10kΩ. If the internal resistance is too large, it means that the liquid junction is blocked and should be dealt with.
(2) Electrode potential check Take a good reference electrode of the same model and the reference electrode to be tested to connect to the input ends of the pH meter, and then insert KCl solution (or buffer solution with pH=4.00) at the same time, the measured The potential difference should be -3~3mV, and the potential change should be less than ±1mV. Otherwise, the reference electrode should be replaced or regenerated.
(3) Appearance inspection The silver-silver chloride wire should be dark brown. If it is off-white, it means that the silver chloride has been partially dissolved.
PH meter maintenance
1. Short-term storage of pH glass electrodes: store in buffer solution with pH=4; long-term: store in buffer solution with pH=7.
2. Cleaning of the pH glass electrode. Pollution of the bulb of the glass electrode may prolong the response time of the electrode. The dirt can be wiped off with CCl4 or soap solution, and then soaked in distilled water for a day and night before continuing to use. When the pollution is serious, it can be immersed in 5% HF solution for 10-20 minutes, rinsed with water immediately, and then immersed in 0.1N HCl solution for a day and night before continuing to use.
3. Glass electrode aging treatment The aging of glass electrodes is related to the gradual change of the adhesive layer structure. Older electrodes have sluggish response, high membrane resistance, and low slope. Etching off the outer adhesive layer with hydrofluoric acid often improves electrode performance. If this method can be used to regularly remove the inner and outer adhesive layers, the life of the electrode is almost unlimited.
4. Storage of the reference electrode The storage solution of the silver-silver chloride electrode is a saturated potassium chloride solution. A high-concentration potassium chloride solution can prevent the precipitation of silver chloride at the liquid junction and maintain the liquid junction in working condition. This method is also applicable to the storage of composite electrodes.
5. Regeneration of the reference electrode Most of the problems of the reference electrode are caused by the blockage of the liquid junction, which can be solved by the following methods:
(1) Soaking liquid junction: use a mixture of 10% saturated potassium chloride solution and 90% distilled water, heat to 60-70°C, immerse the electrode about 5cm, and soak for 20 minutes to 1 hour. This method can dissolve the crystals at the end of the electrode.
(2) Ammonia soaking: When the liquid junction is blocked by silver chloride, it can be soaked with concentrated ammonia water. The specific method is to clean the inside of the electrode, drain the liquid and immerse it in ammonia water for 10-20 minutes, but do not let the ammonia water enter the inside of the electrode. Take out the electrode and wash it with distilled water, and then add the filling liquid again and continue to use it.
(3) Vacuum method: put the hose around the liquid junction of the reference electrode, use a water flow suction pump, and the liquid in the suction part passes through the liquid junction to remove mechanical blockages.
(4) Boiling liquid junction: The liquid junction of the silver-silver chloride reference electrode is immersed in boiling water for 10 to 20 seconds. Note that the electrode should be cooled to room temperature before the next boil.
(5) When the above methods are ineffective, the mechanical method of sandpaper grinding can be used to remove the blockage. This method may cause the grit under grinding to plug into the liquid junction. Causes chronic blockage.
